[glibc/release/2.28/master] <string.h>: Define __CORRECT_ISO_CPP_STRING_H_PROTO for Clang [BZ #25232]

[Florian Weimer <fw at sourceware dot org>]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=ef0051070f820dd5c83a73c0f069cfc4fb373db8

commit ef0051070f820dd5c83a73c0f069cfc4fb373db8
Author: Kamlesh Kumar <kamleshbhalui@gmail.com>
Date:   Thu Dec 5 16:56:04 2019 +0100

    <string.h>: Define __CORRECT_ISO_CPP_STRING_H_PROTO for Clang [BZ #25232]
    
    Without the asm redirects, strchr et al. are not const-correct.
    
    libc++ has a wrapper header that works with and without
    __CORRECT_ISO_CPP_STRING_H_PROTO (using a Clang extension).  But when
    Clang is used with libstdc++ or just C headers, the overloaded functions
    with the correct types are not declared.
    
    This change does not impact current GCC (with libstdc++ or libc++).
    
    (cherry picked from commit 953ceff17a4a15b10cfdd5edc3c8cae4884c8ec3)

Diff:
---
 NEWS            | 1 +
 string/string.h | 3 ++-
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/NEWS b/NEWS
index d488f14..ace1b86 100644
--- a/NEWS
+++ b/NEWS
@@ -72,6 +72,7 @@ The following bugs are resolved with this release:
   [25203] libio: Disable vtable validation for pre-2.1 interposed handles
   [25204] Ignore LD_PREFER_MAP_32BIT_EXEC for SUID programs
   [25225] ld.so fails to link on x86 if GCC defaults to -fcf-protection
+  [25232] No const correctness for strchr et al. for Clang++
 
 Security related changes:
 
diff --git a/string/string.h b/string/string.h
index 150cfd8..22cd0fa 100644
--- a/string/string.h
+++ b/string/string.h
@@ -33,7 +33,8 @@ __BEGIN_DECLS
 #include <stddef.h>
 
 /* Tell the caller that we provide correct C++ prototypes.  */
-#if defined __cplusplus && __GNUC_PREREQ (4, 4)
+#if defined __cplusplus && (__GNUC_PREREQ (4, 4) \
+			    || __glibc_clang_prereq (3, 5))
 # define __CORRECT_ISO_CPP_STRING_H_PROTO
 #endif